Process for making a tungsten carbide die



Aug. 25, 1964 D. w. BREARLEY ETAL 3,145,586

PROCESS FOR MAKING A TUNGSTEN CARBIDE DIE 2 Sheets-Sheet 1 Filed Dec. 19, 1961 m m0 S W W mm mm DDM Y B United States Patent Oflice 3,145,586 Patented Aug. 25, 1964 3,145,586 PRGCESS FUR MAKING A TUNGSTEN I canrsma DIE Donald W. Brearley, Vestal, N.Y., and Donald K. Rex,

San Jose, Calif assignors to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Dec. 19, 1961, Ser. No. 161,341 4 Claims. (#Cl. '76107) The present invention relates to dies such as form part of the die and punch combinations employed in business machines for punching holes into cards, tapes and the like.

In machines of this type such die and punch combinations are subjected to extreme conditions of wear. They are operated in rapid succession, sometimes several thousand times per minute, they must at all times remain at peak efliciency, i.e., operate smoothly without sticking or breaking down, and always provide clearly cut holes without fuzzy edges, and they should last as long as the machine in which they operate because repair or replacements would not only be costly, but also require that operation of the machine be suspended for a substantial period of time with resultant loss of the revenues received for their use.

For dies to meet such extraordinary requirements as to efficiency, wear and durability, it is necessary that their shearing surfaces be made of extremely hard material. In the past they have usually been made from hardened steels, but under the above described conditions of wear dies made from hardened steels of the best quality last rarely longer than a year when they have to be replaced, while machines of the type here under consideration are expected to last at least ten years before any substantial repairs become necessary.

It has, of course, been known that sintered carbides and especially the tungsten carbides are of much greater hardness than the best of hardened steel and it has previously been proposed to use tungsten carbides in the construction of dies. It is difficult, however, on account of the extreme hardness of tungsten carbides and their brittleness, to produce die holes of precise dimensions, especially when the holes are to be relatively small and are to have precisely parallel sides and rectangular corners. The slightest departure of the die holes from a perfect fit with their cooperating punches will not only result in inaccurate and fuzzy punch holes in the processed cards during practical operation of the die and punch combination, but will also cause the punch or the die to chip and thus destroy the punch or the die,or both.

It is an object of ourinvention to provide a die having precisely dimensioned, rectangular die holes, that is capable of withstanding the above described extreme conditions of wear for extended periods of time.

More particularly, it is an object of the invention to provide a die'for use in punching relatively small, precisely rectangular holes, that may be exposed for many years to extreme conditions'of wear in business machines, of thetype referred to, without deterioration in the quality of the holes produced therewith.

A specific object of the invention is to provide a die having precisely dimensioned rectangular die holes, Whose shearing surfaces are formed by a tungsten carbide.

Yet another specific object of the invention is to provide a practical and simple process for producing a die whose shearing surfaces are formed by a tungsten carbide.

An additional object of the invention is to provide a process for producing a die for use in punching precisely dimensioned holes in cards, tapes and the like, whose shearing edges are formed by a tungsten carbide.

These and other objects of the present invention will be apparent from the following description of the accompanying drawings which illustrate certain preferred embodiments thereof, and wherein:

FIG. 1 is a plan view of a die embodying our invention;

FIG. 2 is a fragmentary exploded perspective of the components employed in the construction of the die shown in FIG. 1;

FIG. 3 is a side elevation of one of the components shown in FIG. 2;

FIG. 4 is a cross-section through the components shown in FIG. 2 in properly assembled condition;

FIG. 5 is a cross-section through the assembled die similar to FIG. 4, taken along lines 5-5 of FIG. 1 and viewed in the direction of the arrows associated with said line.

In FIGURES 1 and 2, the reference numeral 10 designates a suitable die base which may be made of steel. Machined into the surface of said baseis a longitudinally extending shallow groove or channel 12, and drilled into the fiat floor 13 of said groove is a series of longitudinally equi-spaced circular holes 14 (FIGURES 2 and 5) that pass through the bottom surface of the base and which serve as ejection channels for the punched-out card fragments during practical use of the finished die.

To construct the actual die upon the base 10, rectangular blocks 16 of a hard tungstencarbide are silver-brazed or'copper-welded upon a bar 18 of steel at equal intervals 20 to form a structure 22 that has somewhat the appearance of a comb or pinion rack as best apparent from FIG. 3. The block ends 24 which define the intervals 20, are now ground by means of silicon-carbide or diamond-impregnated wheels to make these intervals of precisely the length which the finished die holes are to have. To facilitate this operation by providing adequate space for the grinding wheels, the bar 18 may have rounded recesses 26 between the butts 27 to which the blocks 16 are secured, as likewise best apparent from FIG. "3.

The opposite sides 28a and 28b of the blocks 16 are also ground so that all the -blocks may have very precisely the thickness or width which the holes in the completed die are to have.

The floor of the channel 12 in base 10 is now provided with a suitable cement indicated with exaggerated thickness at 30 in FIGURES 4 and 5, such as for instance the epoxy adhesive known under'the trade name Epon 6. Thereupon, the rack-shaped component 22 is inserted into the groove 12 with'its teeth 16 pointingdownwardly with the holes 14 in the floor of the groove and the blocks 16 at'the ends of its teeth rest'upon the areas'between and adjacent to said holes. Likewise-inserted into the groove at either side of the rack bar 22 are tungsten carbidebars 32a and 32b, respectively, of a (vertical) thickness about equal to the (vertical) thickness of the blocks 16. The transverse width of the channel 12 andof bars 321: and 32b is so chosen that thechannel is notc'ompletely-filled by the rack 22 and the bars 32a and 32b in juxtaposition; and into the remaining space between one of said bars and the adjacent sidewall of the channel is forced a barshaped wedge 34 of a soft metal, such as brass to hold the rack 22 and the bars at either side of said rack securely in their proper position relative to each other and relative to the holes 14 in the floor of channel 12.

The described assembly is now subjected to elevated temperatures depending upon the nature of the cement employed, to cure the cement and in this manner secure the bars 32a and 32b and the blocks 16 of rack 22 firmly to the floor of the channel. When the curing is completed and the assembly has cooled, the back of the rack 22, i.e., the steel bar 18 is removed in any suitable manner 3 such as by grinding, and the outer surfaces of the remaining blocks 16 and the side bars 32a and 321) may be ground until they are precisely flush with each other and all form a completely flat surface. The die is now ready for use.

All the shearing surfaces of the finished die are formed by tungsten carbide, namely the blocks 16 and the bars 32a and 32b, and the die holes defined by said shearing surfaces are of precisely the required dimensions. These dimensions are determined by the transverse thickness of the blocks 16 and the distances between the confronting end surfaces 24 of adjacent blocks which were ground to precisely the required dimension before the die was assembled and while the surfaces to be ground were still readily accessible.

Dies constructed in accordance with our invention are as accurate in operation as steel dies, but will outlast comparable steel dies by a factor of more than 10. They do not require repair or replacement during the lifetime of the machines in which they are employed, yet they are of a relatively simple construction, and are easy to manufacture and of reasonable cost. Furthermore, the corners of the holes formed by the carbide pieces are sharp and have no radius or fillet. As far as it is known it is impossible to obtain this by any known method of producing present steel dies.

\Vhile we have described our invention with the aid of certain preferred embodiments thereof, it will be understood that our invention is not limited to specific constructional details shown and described by way of example which may be departed from without departing from the scope and spirit of the invention.

We claim:

1. The method of producing a die having shearing surfaces formed by a hard metal such as tungsten carbide, which comprises forming an aperture in a base of a softer metal than said hard metal, securing a pair of blocks of said hard metal in spaced relation onto a bar of a softer metal than said hard metal, grinding the confronting end surfaces of said blocks to produce an interval of precisely predetermined size, placing the resultant component onto said base with said blocks thereof resting upon said base at opposite sides of said aperture thereof, placing bars of said hard metal onto said base at opposite sides of and in close contact with said blocks, securing said component and said bars permanently in their proper positions and removing the bar of said component.

2. The method of producing a die having shearing surfaces formed by a hard metal such as tungsten carbide, which comprises forming a channel into a base of a softer metal than said hard metal, forming an aperture into the floor of said channel, securing a pair of rectangular blocks of said hard metal in spaced relation onto a bar of a softer metal than said hard metal, grinding the confronting end surfaces and the side surfaces of said blocks to make the interval between and the transverse thickness of said blocks of precisely the required dimensions, placing the resultant component into said channel with said blocks located at opposite sides of said aperture, placing bars of said hard metal into said channel at opposite sides of and in close contact with said blocks, securing said component and said bars in their proper positions relative to each other and to said channel, and removing the bar of said component.

3. The method of producing a die having a rectangular hole with shearing surfaces formed by a hard metal such as tungsten carbide, which comprises forming a channel into a base of a softer metal than said hard metal, forming an aperture into the floor of said channel, securing rectangular blocks of said hard metal in spaced relation onto a bar of a softer metal than said hard metal, grinding the confronting end surfaces of said blocks and the side surfaces of said blocks to make the interval between said blocks and the transverse thickness of said blocks of precisely the required dimensions, placing the resultant component into said channel with said blocks thereof resting upon the channel floor at opposite sides of said aperture, placing bars of said hard metal into said channel onto said floor thereof at opposite sides of and in close contact with the side surfaces of said blocks, driving a wedge between one of said side bars and the adjacent side wall of said channel to hold said side bars and the blocks of said component in their proper positions relative to each other and to said channel, and removing the back bar of said component by grinding.

4. The method of producing a multiple die having rec tangular holes with shearing surfaces formed by tungsten carbide, which comprises forming a channel in a base of steel, forming a row of relatively spaced apertures into the floor of said channel, placing a thermo-setting cement onto the floor of said channel, brazing rectangular blocks of tungsten carbide in spaced relation onto a bar of steel to form a rack-shaped component, grinding the confronting end faces and the outer side surfaces of said blocks to make the intervals between, and the transverse thickness of, said blocks of precisely the required dimensions, plac ing the resultant rack-shaped component into said channel with said blocks thereof resting upon the areas of the channel floor between and adjacent said apertures thereof, placing bars of tungsten carbide of a vertical thickness about equal to the depth of said blocks into said channel onto said fioor thereof at opposite sides of and in close contact with said blocks, driving a wedge between one of said side bars and the adjacent side wall of said channel to hold said side bars and the blocks of said rackshaped component in their proper positions relative to each other and to said channel, subjecting the total structure to a heat treatment to cure said cement and thus render the position of said bars and said blocks within said channel permanent, removing the bar of said rackshaped component by grinding, and grinding the thus exposed upper surfaces of said blocks and the upper surfaces of said side bars until they are precisely flush with each other and form a completely fiat surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,378,562 Lahr June 19, 1945 2,442,153 Van der Pyl May 25, 1948 2,568,152 Hermann Sept. 18, 1951 2,882,759 Altwicker Apr. 21, 1959 2,979,973 Brauchler Apr. 18, 1961 2,990,828 Hoerer July 4, 1961 3,063,310 Connoy Nov. 13, 1962 FOREIGN PATENTS 187,849 Australia Nov. 26, 1956 

1. THE METHOD OF PRODUCING A DIE HAVING SHEARING SURFACES FORMED BY A HARD METAL SUCH AS TUNGSTEN CARBIDE, WHICH COMPRISES FORMING AN APERTURE IN A BASE OF A SOFTER METAL THAN SAID HARD METAL, SECURING A PAIR OF BLOCKS OF SAID HARD METAL IN SPACED RELATION ONTO A BAR OF A SOFTER METAL THAN SAID HARD METAL, GRINDING THE CONFRONTING END SURFACES OF SAID BLOCKS TO PRODUCE AN INTERVAL OF PRECISELY PREDETERMINED SIZE, PLACING THE RESULTANT COMPONENT ONTO SAID BASE WITH SAID BLOCKS THEREOF RESTING UPON SAID BASE AT OPPOSITE SIDES OF SAID APERTURE THEREOF, PLACING BARS OF SAID HARD METAL ONTO SAID BASE AT OPPOSITE SIDES OF AND IN CLOSE CONTACT WITH SAID BLOCKS, SECURING SAID COMPONENT AND SAID BARS PERMANENTLY IN THEIR PROPER POSITIONS AND REMOVING THE BAR OF SAID COMPONENT. 